Suggestion: If strife gets too high/goes over a certain limit. The public starts to demand you to restore order if you are in government and/or control Prussia and failure to do so (You doing nothing or your actions fail to restore order) results in decreased SPD/republic support.
For examples of those actions can be something like:
-Use interior ministry to ban/persecute a paramilitary
-Increase police presence/patrols
-Use loyal reichswehr to enact martial law(?)
My examples aren't super thought out but I hope it gets the point across.